R&D Portfolio - Research Goal 4.6:
Prevent hearing loss from exposure to ototoxic chemicals alone or in combination with noise

Issue
Ototoxic chemicals are chemicals hazardous to hearing. Some of them are capable of damaging the auditory mechanism alone. Others may exacerbate the damaging effects of noise on hearing. Ten million workers are potentially exposed to ototoxic solvents.[45]

The effects of ototoxic chemical exposure in the workplace have been neglected. Currently hearing conservation practices focus on noise and do not take into account the risks of ototoxic chemicals. Hearing conservation programs do not consider such exposures when defining workers’ eligibility for the program. Current exposure prevention strategies can be insufficient to protect workers simultaneously exposed to ototoxic chemicals and noise.

Auditory effects are not considered when chemical exposure regulations are adopted, and chemical effects are not considered when noise exposure regulations are made. Only workers who are exposed to noise levels above 85 dB(A) are required by OSHA to have their hearing tested periodically. The audiometric configuration of noise-induced hearing loss and chemical-induced hearing loss can be identical. Careful analyses of these results must be performed and attention given to all the exposure conditions to ensure that hearing disorders are not being erroneously attributed solely to noise.

Approach
As early as 1988, the HLR program identified the need to “determine…the degree to which noise interacts with other agents… to affect hearing.” The following sub-goals were adopted:

Identify specific ototoxic chemicals or classes of chemicals of concern and characterize the risk;

Bring this risk to the attention of workers, public health professionals, and policy makers; and